Power plants – Pressure fluid source and motor – Condition responsive control of motive fluid flow
Patent
1996-03-20
1998-10-13
Lopez, F. Daniel
Power plants
Pressure fluid source and motor
Condition responsive control of motive fluid flow
60465, 60471, 91523, 91529, 91DIG1, F16D 3102
Patent
active
058195360
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a hydraulic circuit for controlling a plurality of hydraulic motors, said circuit comprising a reservoir for hydraulic fluid, a reversible pump connected therewith and driven by an electric motor, as well as a valve device for controlling the hydraulic fluid flow to the various motors.
Such a hydraulic circuit is disclosed in EP-A-0 425 156.
For the control of a plurality of hydraulic motors, in particular hydraulic piston cylinder devices, it has been usual to provide each piston cylinder device with a valve device adapted to be actuated according to a desired program. With a double acting piston cylinder device such valve device usually comprises two electro-valves, which may be ball seat valves of the 3/2 type. Such valves are especially designed for high procures and leakage proof operation and are relatively expensive. In most cases, where a plurality of piston cylinder devices has to be controlled from a common hydraulic fluid source, this is not considered as a drawback, as in such cases relatively heavy piston cylinder devices are involved, which are expensive as such, whereas the pump pressures are generally not very high.
In other cases such as with the hydraulic circuit disclosed in above mentioned EP-A-0 425 156, where relatively light weight piston cylinder devices have to be actuated in a desired sequence, however, the drawback connected with the electro-valves counts very heavily. For the limited space, which is usually available for a accommodating the piston cylinder devices and the respective control unit, necessitates the use of extra high pump pressures.
As an other example of such a case reference is made to NL-A-9200628 (EP-A-0 565 190). In this case three (pairs of) piston cylinder devices are applied, which have to be actuated in a certain sequence. In such a case one speaks of a hydraulic circuit with a plurality of (three) cylinder functions. In the latter circuit the actuation is usually effected by a pump having one direction of rotation, in cooperation with a control valve block, that comprises two electro-valves for each (double acting) cylinder function.
In these cases the valves are very expensive in proportion to the relatively compact piston cylinder devices, and make a hydraulic device for opening and closing a foldable cover with a vehicle of the cabriolet-type very expensive and even more expensive in proportion to the number of cylinder functions to actuate.
More generally separate electro-valves are required for each required cylinder function. In the example of EP-A-0 425 156 where three (pairs of) double acting cylinders and consequently six control outputs are involved, there is a need for four electro-valves, whereas in the example of EPA-0 565 190 three double acting cylinders and consequently six required control outputs and six electro-valves are involved.
The invention aims at providing a hydaulic circuit, in which a relatively large number of cylinder functions with associated outputs may be obtained with a relatively small number of electro-valves.
In accordance with one aspect of the invention there is provided a hydraulic circuit for controlling a plurality of hydraulic motors, said circuit comprising a reservoir for hydraulic fluid, a reversible pump connected therewith and driven by an electric motor, as well as a valve device for controlling the hydraulic fluid flow to the various motors, characterized in that each of the suction/pressure sides of the reversible pump is connected to a respective output of a suction shuttle valve which is connected by its input to the reservoir, each of the suction/pressure sides of the reversible pump is further connected to a different one of the two inputs of an OR-valve and with one of the inputs of at least two AND-valves respectively, the out of the OR-valve being connected to the fluid inlet of at least one electro-valve, the output or outputs of which is or are hydraulically connected with the other inputs of the at least two AND-valves whereby each outlet of the at least two AND-valves a
REFERENCES:
patent: 3178886 (1965-04-01), Watson
patent: 3866421 (1975-02-01), Kersten et al.
patent: 4433612 (1984-02-01), Spielvogel et al.
patent: 4489643 (1984-12-01), Spielvogel et al.
patent: 4761953 (1988-08-01), Rosman
Ing. Gunter Ortmann, "Fluidics-Schaltplane und -Schaltungen", Olhydraulik und Pneumatik, vol. 14, No. 5, May 1970, pp. 211-215.
Applied Power Inc.
Lopez F. Daniel
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